Travelled with

First story

Last story

Hex was a male nurse in Liverpool a few years in the future. He got mixed up in a Cyberplot that the Doctor and Ace were investigating at his hospital, and the he and Ace saved each other from supersoldiers, so the Doctor had only one choice—wipe his memory and dump him. But Ace noticed that he'd admired her thorax, so she convinced the Doctor to take him along instead.

He turned out to be pretty useful, but he went through a lot of serious VNA-level companion-torture and then left. Of course eventually, like everyone in Big Finish after they ran out of ideas, he came back and left and got his memory wiped and died and came back as an alternate version of himself and so on a few more times.

Hex is also the orphan baby of that nice vampire girl from the Six/Evelyn audios, which was treated like a big (oh my god!) spoiler, but it actually made no difference to what was going on. But it was some nice closure for Evelyn's last story, and they made use of it later a few times, so, whatever, Bravo Russell if you must.

If you want to know which gap in the Seven/Ace timeline BF crammed this one into—well, Gary Russell produced these stories, and he's insanely obsessed with continuity, and even he's given up on making Ace's timeline work once they shoehorned Raine in. So, naturally, the TARDIS Data Core gives you an answer anyway.

Sylvester and Sophie hadn't acted in years and thought that the key was to shout each line as loud as possible, and the fanboy directors were all too "oh wow it's really Sylvester McCoy" to tell them otherwise, so they needed someone else to carry the emotional weight of the stories. So BF hired a soap opera guy famous for being handsome, because that's really important in audios.